1. Field of the Invention
The present invention relates to the production of extrudable pre-ceramic polycarbosilanes, and, more especially, to the production of extrudable polycarboxilanes by intimately contacting a crude polycarbosilane containing a fraction of high molecular weight polymers with ethyl acetate and recovering dissolved extrudable polycarbosilanes from such ethyl acetate selective solvent.
2. Description of the Prior Art
It is known to this art to prepare silicon carbide fibers from polysilanes, by first rearranging such polysilane into polycarbosilane, next extruding the polycarbosilane in fibrous form and then converting the polycarbosilane fibers into ceramic silicon carbide fibers.
The heretofore known processes for rearranging a polysilane into a polycarbosilane result in the production of a heterogeneous polycarbosilane, i.e., a polycarbosilane that is heterogeneous both relative to its molecular weight distribution and to its degree of branching. Thus, a polycarbosilane is produced that is difficult to extrude. Hence, it is necessary to treat this raw polycarbosilane such as to provide a product that is easy to extrude and thereafter easily converted into silicon carbide ceramic material.